1. Technical Field of the Invention
The present invention relates to a tool for a semiconductor manufacturing apparatus and a method for using the same, more particularly, a tool for a semiconductor manufacturing apparatus, used for a chemical vapor deposition device and designed to prevent etching damage at the time of reproduction, and a method for using the same.
2. Description of the Related Art
Since a semiconductor substrate is given a prescribed treatment, heavy metal pollutant generally contaminate a tool that supports the substrate inside a treatment container, and so the tool needs to be cleaned before being used. A method of cleaning a tool made of silicon carbid (SiC) and used for a heat treatment process is cited as an example here. After the tool made of silicon carbide (hereinafter xe2x80x9cSiCxe2x80x9d) is cleaned with hydrochloric acid and the pollutants are removed from the surface thereof, it goes through a 3-hour-long oxidization process at a temperature of 1270xc2x0 C. to coat the surface of SiC with an oxidized film. Next, a 48-hour-long heat treatment in a nitrogen atmosphere is applied to the tool to form a silicon nitride film on the interface of the SiC surface and silicon oxidized film. Since a sufficiently dense silicon nitride film is formed on the SiC cleaned as explained above, the pollutants contained in the SiC will n disperse out of it and exert an adverse effect on the semiconductor substrate. (Japanese Laid-open Patent Publication No. 123887 of 1988)
Conventionally, with respect to a method for using a tool for device of the low pressure chemical vapor deposition, when a nitride film is formed on the semiconductor substrate by the LPCVD device, a nitride film and impurities in a chamber (hereinafter referred to as xe2x80x9cnitride film and the likexe2x80x9d) also adhere to and deposit on the tool. After the deposited nitride film and the like on the tool reach a prescribed thickness of the accumulated films, wet etching is administered to the tool for the purpose of removing the nitride film and the like on the tool and reproducing and enabling the tool to be repeatedly used.
However, in the abovementioned method, if the thickness of the nitride film and the like adhered to and deposited on the tool varies from place to place, the remaining films such as the nitride films are easily generated where the films are thicker, even after etching is conducted. Therefore, to prevent such films from remaining, additional etching is generally carried out.
FIGS. 1A through 1C are schematic views of a tool used for the LPCVD device in the prior art. When the tool for the LPCVD device is used, the tool is first set in a tool-cleaning tank for initial cleaning. For the 30-minute-long initial cleaning mixed solution of HF, HNO3 and H2O is used.
Next, when the tool 14 is used in order to support a semiconductor substrate on it, for example, and to deposit a nitride film 3 on the semiconductor substrate, the nitride film 3 is also adhered to and deposited on the tool 14, as shown in FIG. 1A. After the thickness of the accumulated nitride film 3 deposited on the tool 14 reaches a prescribed thickness, the tool 14 is detached from the device. Subsequently, the tool 14 on which the nitride film 3 is deposited, is detached from the LPCVD device, and etching is carried out by using a mixed solution of HF and HNO3 to reproduce the tool 14.
As shown in FIG. 1B, if the thickness of the nitride film 3 deposited on the tool 14 is locally uneven, not all of the nitride film 3 can be removed by etching on the parts where the nitride film 3 is thick. Accordingly, a protruded part 3a of the nitride film remains on the surface of the tool 14 reproduced by etching. In order to remove such protruded part 3a of the nitride film remaining on the tool 14, additional etching is carried out and the tool 1 is reproduced.
However, by the additional etching applied to the abovementioned tool 14, the following problem arises. Specifically, on the parts where the nitride film 3 formed on the tool 14 is relatively thin, removal of the nitride film 3 has already been completed and the surface of the tool 14 is exposed. Therefore, additional etching results in over etching to the tool 1. The surface of the tool 1 is partially excessively etched, as shown in FIG. 1C, causing the tool 14 to be damaged and the life thereof is shortened.
It is an object of the present invention to provide a tool for a semiconductor manufacturing apparatus which is reproducible by etching without being damaged, and a method for using the same.
A tool of the semiconductor manufacturing apparatus according to the present invention is used for forming a film on the semiconductor substrate. The tool of the semiconductor manufacturing apparatus comprises a base portion, and a coating film coated on the surface of said base portion. Etching speed of the coating film is faster than that of a film to be formed on said semiconductor substrate.
A method for using the tool for the semiconductor manufacturing apparatus according to the present invention, comprises the steps of forming a coating film, the etching speed of the coating film being faster than that of a film to be formed on a semiconductor substrate, on the surface of a base portion, supporting the semiconductor substrate by said base portion and forming a film on said semiconductor substrate, and removing said coating film of the surface of said base portion and reproducing said base portion by giving wet etching to said base portion.
In the present invention, the film, whose etching speed is faster than that of the film to be formed on the semiconductor substrate, has already been coated on the surface of the tool. The film to be formed on the semiconductor substrate is called a production film. If this tool is used in the semiconductor manufacturing apparatus and a production film is formed on said semiconductor substrate, the production film is also adhered to the coating film formed on the surface of the tool. After the production film reaches a prescribed thickness, the tool is detached from the device and is reproduced by wet etching. In this procedure, first, on the parts where the production film, adhered to the coating film, is thinner than other parts, the coating film underlying the production film is exposed. Since the exposed coating film is etched faster than the production film it is selectively etched and removed. While the coating film is being removed, the production film, which is adhered to the coating film, is also peeled and removed, together with the coating film. Since no production film can remain on the tool, additional etching required in the prior art is no longer necessary and the problem of over etching of the tool can be resolved.